SYNTHESIS OF STEROIDAL PLANT-GROWTH REGULATORS .23. STEREOSELECTIVE SYNTHESIS OF CRINOSTEROL AND BRASSICASTEROL FROM HYODEOXYCHOLIC ACID

Synthesis of crinosterol (1) and brassicasterol (2), Which are preferential starting materials for syntheses of brassinolide (3) and 24-epi-brassinolide (4), have been achieved, starting from the 20-carbonaldehyde (6) obtained from the hyodeoxycholic acid (5). The overall yield of 1 and 2 is 48-57% and 52-54%, both in six steps, respectively. The key step of these syntheses is the Claisen rearrangement.